"In The Grim Darkness Of The Far Future There Is Only War"
Warhammer 40k is set in a Universe where no one is safe from the horrors of space. The Imperium of man struggles to hold its borders or protect its citizens from the the alien, the mutant and the heretic. The human race is no longer a progressive race, most of the weapons and vehicles they use date back to the "Dark age of Technology" long before the days of the Emperor. Technological advance is at standstill and much has been forgotten, never to be recovered.
In this dark millenia danger lurks behind every corner, and it is the holy duty of the Inquisition to guard and purge the threats within and without the Imperium. Take the role of Malachias Kane, Young Inquisitor under the command of Lord Inquisitor Dante, warring agains the notorious Chaos sorcerer Bathomeos. It is your mission to rendevouz with allies, and deliver the final piece to the plan to bring the Chaos scum under the Emperor's hammer.

/You better watch out, you better not pout! There might be a techpriest somewhere about, Me-chanus is coming to town!

/They have a big list, of criminal scum, who've rebelled against the Imperium!
Me-chanus is coming to town!

/They'll turn you into machines, to mindless, gutless slaves.
They'll use their ancient wisdom, to use you as their knaves!
~So~
/You better not whine, you better not fight, or they will break you, with all their might!
Me-chanus is coming to town!
Me-chanus is coming to to---wn!

I think that making the white parts a bit more yellow/brown would do the trick. That and a less cheerful, not as vibrant, red colour.

Perhaps having no white on the sleeves as well and perhaps make the edges of the cloth more ragged/torn (Nothing is new in the year 40.000 after all) would complete the look, make it look more sinister.